Support multiple --feature-gates flags in the command line

staging/src/k8s.io/apiserver/pkg/util/feature/feature_gate.go

@@ -50,10 +50,7 @@ var (
 	}
 
 	// DefaultFeatureGate is a shared global FeatureGate.
-	DefaultFeatureGate = &featureGate{
-		known:   defaultFeatures,
-		special: specialFeatures,
-	}
+	DefaultFeatureGate FeatureGate = NewFeatureGate()
 )
 
 type FeatureSpec struct {
@@ -75,43 +72,9 @@ const (
 type FeatureGate interface {
 	AddFlag(fs *pflag.FlagSet)
 	Set(value string) error
-	Add(features map[Feature]FeatureSpec)
+	Enabled(key Feature) bool
+	Add(features map[Feature]FeatureSpec) error
 	KnownFeatures() []string
-
-	// Every feature gate should add method here following this template:
-	//
-	// // owner: @username
-	// // alpha: v1.4
-	// MyFeature() bool
-
-	// owner: @timstclair
-	// beta: v1.4
-	AppArmor() bool
-
-	// owner: @girishkalele
-	// alpha: v1.4
-	ExternalTrafficLocalOnly() bool
-
-	// owner: @saad-ali
-	// alpha: v1.3
-	DynamicVolumeProvisioning() bool
-
-	// owner: @mtaufen
-	// alpha: v1.4
-	DynamicKubeletConfig() bool
-
-	// owner: timstclair
-	// alpha: v1.5
-	StreamingProxyRedirects() bool
-
-	// owner: @pweil-
-	// alpha: v1.5
-	ExperimentalHostUserNamespaceDefaulting() bool
-
-	// owner: @davidopp
-	// alpha: v1.6
-	// TODO: remove when alpha support for affinity is removed
-	AffinityInAnnotations() bool
 }
 
 // featureGate implements FeatureGate as well as pflag.Value for flag parsing.
@@ -137,10 +100,21 @@ func setUnsetAlphaGates(f *featureGate, val bool) {
 // Set, String, and Type implement pflag.Value
 var _ pflag.Value = &featureGate{}
 
+func NewFeatureGate() *featureGate {
+	f := &featureGate{
+		known:   map[Feature]FeatureSpec{},
+		special: specialFeatures,
+		enabled: map[Feature]bool{},
+	}
+	for k, v := range defaultFeatures {
+		f.known[k] = v
+	}
+	return f
+}
+
 // Set Parses a string of the form // "key1=value1,key2=value2,..." into a
 // map[string]bool of known keys or returns an error.
 func (f *featureGate) Set(value string) error {
-	f.enabled = make(map[Feature]bool)
 	for _, s := range strings.Split(value, ",") {
 		if len(s) == 0 {
 			continue

staging/src/k8s.io/apiserver/pkg/util/feature/feature_gate_test.go

@@ -119,9 +119,11 @@ func TestFeatureGateFlag(t *testing.T) {
 	}
 	for i, test := range tests {
 		fs := pflag.NewFlagSet("testfeaturegateflag", pflag.ContinueOnError)
-		f := DefaultFeatureGate
-		f.known[testAlphaGate] = FeatureSpec{Default: false, PreRelease: Alpha}
-		f.known[testBetaGate] = FeatureSpec{Default: false, PreRelease: Beta}
+		f := NewFeatureGate()
+		f.Add(map[Feature]FeatureSpec{
+			testAlphaGate: {Default: false, PreRelease: Alpha},
+			testBetaGate:  {Default: false, PreRelease: Beta},
+		})
 		f.AddFlag(fs)
 
 		err := fs.Parse([]string{fmt.Sprintf("--%s=%s", flagName, test.arg)})
@@ -140,15 +142,45 @@ func TestFeatureGateFlag(t *testing.T) {
 	}
 }
 
+func TestFeatureGateOverride(t *testing.T) {
+	const testAlphaGate Feature = "TestAlpha"
+	const testBetaGate Feature = "TestBeta"
+
+	// Don't parse the flag, assert defaults are used.
+	var f FeatureGate = NewFeatureGate()
+	f.Add(map[Feature]FeatureSpec{
+		testAlphaGate: {Default: false, PreRelease: Alpha},
+		testBetaGate:  {Default: false, PreRelease: Beta},
+	})
+
+	f.Set("TestAlpha=true,TestBeta=true")
+	if f.Enabled(testAlphaGate) != true {
+		t.Errorf("Expected true")
+	}
+	if f.Enabled(testBetaGate) != true {
+		t.Errorf("Expected true")
+	}
+
+	f.Set("TestAlpha=false")
+	if f.Enabled(testAlphaGate) != false {
+		t.Errorf("Expected false")
+	}
+	if f.Enabled(testBetaGate) != true {
+		t.Errorf("Expected true")
+	}
+}
+
 func TestFeatureGateFlagDefaults(t *testing.T) {
 	// gates for testing
 	const testAlphaGate Feature = "TestAlpha"
 	const testBetaGate Feature = "TestBeta"
 
 	// Don't parse the flag, assert defaults are used.
-	f := DefaultFeatureGate
-	f.known[testAlphaGate] = FeatureSpec{Default: false, PreRelease: Alpha}
-	f.known[testBetaGate] = FeatureSpec{Default: true, PreRelease: Beta}
+	var f FeatureGate = NewFeatureGate()
+	f.Add(map[Feature]FeatureSpec{
+		testAlphaGate: {Default: false, PreRelease: Alpha},
+		testBetaGate:  {Default: true, PreRelease: Beta},
+	})
 
 	if f.Enabled(testAlphaGate) != false {
 		t.Errorf("Expected false")